Extending Smart RAMPS Tips and Advice

This is my first post, but been following the forum for a few weeks now, but I have decided to try and make myself my own 3D printer based on the Hypercube and Hypercube Evolution as a CoreXY with dual Z motor lift, or a single Z using a non-captive Motor and centering it at the middle of the underside of the heatbed (I haven't decided just yet which one, I need to see advantages and disadvantages of both systems)
[www.thingiverse.com], [www.thingiverse.com]

Anyways I want to go one step further than being just a single extruder system and so I thought of using an E3D Kraken quad hotend in a Bowden configuration. With extra features added such as:
Filament Sensors for 4 filaments (Either 'run-out' or 'complete' with filament thickness and run-out. Again not decided as I have to see if MK4duo has this feature)
5 thermistor sensors (one for each hotend and one for the heated bed)
7 Stepper Drivers using TMC 2208 modules
A Graphical Mono Display (the one which comes with Smart RAMPS [www.aliexpress.com])
Nexiton 7" Capacitive Touch Display (apparently it works with MK4Duo Firmware, uses the TX/RX pins available of wifi pins on the Graphical Mono Display)
Heated Bed (220V AC heated bed using Solid State Relay)
Inductive Sensor (For Autobed alignment)
4 Indivisual Hotend (Using E3D Kraken)

Although this is a lot features to put onto a Smart RAMPS, I have noticed that there is: 3 Analogue Pins not in use and 17 Digital Pins Left available. Also I2C available. With that, I concluded that I would need to use two Analogue Pins for the extra two hotends Thermistors, 9 Digital Pins for the two extra Stepper Driver modules, two extra Hotend heater power and an inductive sensor.

My question is:
1) Has anyone else made an extension board for the Smart RAMPS yet?
2) Does anyone know the exact pin layout dimensions of the Smart RAMPs and the pololu module so I could create the plugin daughter board?
3) Anyone be interested on schematics and PCB layout once I make it so I can share it with everyone?
4) Any other request to layout other things onto the board? We have 3 Analogue and 17 Digital Pins here available.
5) How would I assign the pins on MK4Duo once I created the daughter board?
6) Whats your impressions of the Smart RAMPs, info on this board was a bit hard to find on peoples reviews, it gets overshadowed by RAMPs 1.4 for the Mega 2560

I've got loads of other questions about building a 3D printer, but I think it was best to start on the brains of the printer and work myself out from there

For for the option I was going for the cost end up being for:
Andriod Due (I already have one)
Smart RAMPs + Mono display (£34)
Plus stepper motors drivers (https://www.aliexpress.com/item/5pcs-TMC2208-Stepping-Motor-Mute-Driver-Stepstick-Power-Tube-Built-in-Driver-Current-1-4A-Peak/32852267476.html) (If I buy 10 £43.84 have some spare)
Custom daughter board, which I will design and only cost me $5 to make 10 boards (as long as it below 10x10cm and two layers) and $20 to ship
and the components which will cost no more than £10.
And a Nexiton 7" Display for $108.00 (https://www.itead.cc/nextion-nx8048k070-011r-011c.html)

All in all it would then it would cost me about £185 (give or take exchange rates), and that the cost saving can then go to buying other parts.

Plus designing a PCB board is not a difficult thing to do, now that I have found the BRD files from the Smart RAMPs wiki on reprap, I will probably finish daughter board design over night if needed. This can then add two extra onto the Smart RAMPs allowing it to expand to four filament material extruding.

To be honest I want to learn as I build, for me just building a printer is not what motivates me, its learning as I go and improving things which can help benifit me but also share with others, this is why I firstly came to this forum to chat, learn and share my finding and hopefully give an answer to others.